The present invention relates to the vacuum art and practice of dehydrating and puffing fruits and vegetables, and in particular to the use of heated edible oils as a liquid heat transfer agent to effect rapid evaporation of natural moisture of the comestible in a vacuum environment.
In the past, much hand labor has been required, and volume of output has been small. The present invention is addressed to automation and the production of large quantities of output of puffed, crisp product of high quality, and is an improvement in the process covered in my U.S. Pat. No. 4,769,249 to be granted Sept. 6, 1988. The manufacture of the first samples of such comestibles is described in my U.S. Pat. Nos. 2,283,302, 2,110,184, 4,006,260, 4,566,376 and 4,769,249. The latter patent claims a system for automation.
In this art,.the comestible is enclosed in a vacuum vessel in which the absolute pressure is reduced to only a few millimeters of mercury measure or torr. Then heated edible oil is made to contact the comestible without causing caramelization of the natural sugars or deleterious change of flavor or color. The oil is circulated through a heater and returned to act as a heat transfer liquid overcoming the latent heat of evaporation of the natural moisture. When the moisture content has been reduced to about two percent, the oil is cooled and this cools and hardens the fruit and fixes the puffed structure that has resulted from rapid evaporation. Then the cool oil is drained away. Centrifugal action may be used to assist drainage. The de-oiled fruit is returned to normal atmosphere without collapsing the newly generated pores.
In my prior patents, I use a relatively high temperature in the range of between about eighty degrees Centigrade to about one-hundred degrees Centigrade for the cooking oil in order to maintain high efficiency. These higher temperatures frequently result in some loss in natural flavor and some brown tinting due to caramelization.
I have discovered that, through an improved process, as set forth herein, I can obtain superior product with improved flavor and appearance.